06-30-14: Atmasphere
That is quite impressive to get that sort of bandwidth out of an SET of that sort of power! Do you know the configuration- by any chance is it a parafeed circuit?
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I designed and built it, so I'm very familiar with the configuration. It's a series feed two-stage direct-coupled single-ended design; no parafeed. The driver tube (the excellent Russian 6E5P tetrode, triode strapped) has an active gyrator/mu follower load to supply the grid current demanded when the amp goes into A2.
You can see the LTSpice schematic in the first post of this thread:
The Midlife Crisis
I simulated both parafeed and series feed as I was brainstorming this build; both have their advantages and disadvantages as you well know, but I decided to go for broke and make it series feed, which required me to get very expensive custom gapped transformers from Monolith (these are now part of their Summit line). I could have used a less expensive, smaller transformer with parafeed but then I'd need a custom plate choke to handle the voltage (which could swing to nearly 5000V!) and a high-voltage capacitor as well so it ends up not being much of a cost or weight advantage for parafeed. I opted for the simplicity of series feed.
As I said, the OPT is massive to be able to handle such high power; here's a picture of the wound core before strapping and potting, with an ECC83 tube for reference:
Core
Each monoblock weighs about 180lbs, and is built on a Landfall Systems aluminum chassis.
That is quite impressive to get that sort of bandwidth out of an SET of that sort of power! Do you know the configuration- by any chance is it a parafeed circuit?
---------------------------------------------------------
I designed and built it, so I'm very familiar with the configuration. It's a series feed two-stage direct-coupled single-ended design; no parafeed. The driver tube (the excellent Russian 6E5P tetrode, triode strapped) has an active gyrator/mu follower load to supply the grid current demanded when the amp goes into A2.
You can see the LTSpice schematic in the first post of this thread:
The Midlife Crisis
I simulated both parafeed and series feed as I was brainstorming this build; both have their advantages and disadvantages as you well know, but I decided to go for broke and make it series feed, which required me to get very expensive custom gapped transformers from Monolith (these are now part of their Summit line). I could have used a less expensive, smaller transformer with parafeed but then I'd need a custom plate choke to handle the voltage (which could swing to nearly 5000V!) and a high-voltage capacitor as well so it ends up not being much of a cost or weight advantage for parafeed. I opted for the simplicity of series feed.
As I said, the OPT is massive to be able to handle such high power; here's a picture of the wound core before strapping and potting, with an ECC83 tube for reference:
Core
Each monoblock weighs about 180lbs, and is built on a Landfall Systems aluminum chassis.